Abstract

Using the planar optical waveguide geometry, coherent anti-Stokes Raman scattering becomes a very sensitive type of vibrational spectroscopy for the study of surface structure and chemistry. The waveguide structure consists of a film (about one micron thick) of a material such as ZnO on a fused silica substrate. Laser fields can be constrained by total internal reflection such that they propagate through the film as guided waves. The concept is to perform CARS using the evanescent fields extending above the waveguide surface. The key to making this a very attractive form of surface spectroscopy is the establishment of an interference condition within the film, thereby eliminating the contribution from the vibrationally resonant or nonresonant third order susceptibility of the film itself. The remaining signal consists mainly of the signal from the surface and any surface adsorbates. With this technique, the Raman spectrum of interfacial species can be observed over the 0 to 4000 cm^-1 range under environments ranging from UHV to condensed phases.

© 1987 Optical Society of America